Needle covering mechanism, needle holder and hypodermic syringe

摘要

A needle covering mechanism (1) for a hypodermic syringe (2) comprises a protective cover sleeve (4) which is movable between a retracted position in which a needle (27) is exposed and an extended position in which the needle (27) is covered. A retainer (9) comprises first detents (16) which by means of a spacer (11) is forced to engage indentations (25) in the cover sleeve (4), to prevent a movement of the cover sleeve (4) towards the extended position. The spacer (11) is made from a material which after some time in contact with an injectant loses its mechanical strength, and some time after filling the syringe (2) with an injectant, the spacer (11) deform, the first detents (16) slip out of the indentations (25) in the cover sleeve (4), and a spring (8) forces the cover sleeve (4) to the extended position.